In a signal transmission line, an electrostatic discharge (ESD) protection diode is provided to protect internal electronic circuits from ESD events. The ESD protection diode must have a lower capacitance as signal frequency increases.
In the ESD protection diode having an inter-terminal capacitance less than 1 pF, an electric circuit typically called a “crowbar circuit” is used. However, in recent years, the ESD protection diode has been required to be miniaturized.